China and Russia have said negotiations are the only way of easing tension over Iran's nuclear programme, following Tehran's offer of talks on the issue.

But France has insisted that talks can restart only if Tehran halts its uranium enrichment programme first.

Iran has offered "serious talks" with six world powers, in response to a UN resolution which set a deadline of 31 August for the programme to be halted.

It faces possible sanctions amid claims it is making a bomb, which it denies.

Tehran maintains it has a right to civilian nuclear technology.

The US, UK, Russia, China, France and Germany have offered Iran a package of incentives - including help with civilian nuclear technology - in exchange for suspending enrichment.

Iran's leaders insist the nuclear programme has a civilian purpose

Iran's chief nuclear negotiator, Ali Larijani, said on Tuesday that his country was ready for "serious talks" on the issue - but did not give any more details of its response to the offer.

Beijing said it hoped all parties would show calm, patience and flexibility so that negotiations could be resumed, and said it was "carefully studying" Iran's reply.

"China has always believed that seeking a peaceful resolution of the Iranian nuclear issue through diplomatic talks is the best choice and in the interests of all parties concerned," the Chinese foreign ministry said.

The Iranians know the rules of the game: first a suspension of sensitive nuclear activities

Philippe Douste-BlazyFrench Foreign Minister

Russia echoed the Chinese stance, stressing its commitment to a negotiated solution to the crisis over Iran's nuclear programme.

The US gave no immediate reaction to Iran's response. "We're giving it careful consideration and a careful review, as it deserves," White House spokeswoman Dana Perino said.

But in Paris, French Foreign Minister Philippe Douste-Blazy said fresh talks were dependent on Tehran first suspending its nuclear activities.

"As we have said all along, and as Mr Larijani well knows, the return to the negotiating table is tied to a suspension of its uranium enrichment activity," he said.

"The Iranians know the rules of the game: first a suspension of sensitive nuclear activities."

Sanctions threat

Although Mr Larijani has spoken of "serious talks", what the Security Council needs to know is whether Iran is willing to suspend uranium enrichment by 31 August or not, says the BBC News website's world affairs correspondent, Paul Reynolds.

While the US has been playing poker in the region, Iran has been playing chess

If it is not, or gives no clear response on this, the US and its allies will take it as a "no" and will press for sanctions, though these would need a separate council decision, our correspondent adds.

Iranian officials had previously said the response would address ambiguities over its right to nuclear technology.

Enriched uranium is used as fuel for nuclear reactors, but highly enriched uranium can also be used to make nuclear bombs.

Iran points out that as a signatory to the nuclear Non-Proliferation Treaty (NPT) it is entitled to a nuclear power programme and says it has broken no rule.

But the Western powers accuse Iran of concealing an enrichment programme, and Washington has refused to rule out military action.

Iranian leverage

Meanwhile, a report by UK-based think tank Chatham House says Iran can afford to continue equivocating in the dispute over its nuclear programme because of its regional supremacy.

"The US-driven agenda for confronting Iran is severely compromised by the confident ease with which Iran sits in the region," the report says.

The report argues that Iran has emerged as the biggest beneficiary of the US-led "war on terror" in the Middle East.

Recent US-led wars have "eliminated two of Iran's regional rival governments - the Taleban in Afghanistan and the Saddam Hussein regime in Iraq in April 2003".

The report says the US "has failed to replace either with coherent and stable political structures".

Iran wields more influence than the US in Iraq, the report said, and is also "a prominent presence" in Afghanistan.